Exergy Analysis and Experimental Study of a Vehicle-Mounted Heat Pump–Assisted Fluidization Drying System Driven by a Diesel Generator

Abstract

In light of present development of Chinese agricultural processing technology, a vehicle-mounted grain drying system driven by a diesel generator has been developed to work interregionally with the existing combine harvester to harvest and dry grain simultaneously. A horizontal multichamber fluidized bed was chosen as the drying chamber, and a vapor compression heat pump (R134a as refrigerant) supplies heat for this system. The latent heat of steam discharged from the fluidized bed's forepart is recovered by the heat pump evaporator, and ambient air is blown into the rear part to recover sensible heat from the postdrying grain. Heat exchangers are installed along the air duct to recover the waste heat from the cooling water and flue gas in the diesel generator, to increase the primary energy ratio (PER). The exergy efficiency of the semiclosed heat pump was 29.2% based on the mathematical model. Performance tests of the drying equipment showed that the actual PER of the drying system was 1.19, the coefficient of performance (COP) of the heat pump was 4.38, the actual specific diesel consumption was 0.081 (kg diesel)/(kg water), and the designed targets were mostly achieved.